Computing slide-rule.



. result read directly from the instrument.v I am not aware that it has everV Rules,

.bodiment of the invention HENRIK GRNDAHL, OF CHICAGO,

ILLINOIS, AssIeNoR'To BURGESS a SAUERBERG, 0F GRAND RAPIDS, MICHIGAN, A corARTNERsIIIP.

COMPUTING SLIDE-RULE.

Specification of Letters Patent. Application led. August 14, 1905. Serial No. 274,036.

Patented April 14, 1908.

To all whom it may concern:

Be it known that I, HENRIK GRNDAIIL, a cltizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Computing Slideof which the following is a specification. 4

This invention relates to improvements in computing slide rules and it has for its object to provide a device of the character referred to suitable for performing with facility additions and' subtractions particularly when such computations involve fractions.

Another object of the inventionis to provide an improved construction enabling the rule to be made cheaply and reliably and when made characterlzed by compactness and simplicity of manipulation. I 'am aware that slide rules have been made in great variety but I know of none so constructed and arranged that by simply shifting asingle slide progressively along the main rule a series of4 additions or subtractions, or both, may be performed and the Moreover been proposed to depart from actual umts of measurement. in laying out or graduating a slide rule and substitute enlarged scales -p which enable the operator to easily read measurements which are in fact'microscopical and this without thev aid of a magnifyinginstrurnent and without danger of misreading. These and other' improved results are accomplished by my present invention which -will be readily understood from the following description, reference Whic Figure 1 is a plan view4of a referred ems own folded. Fig. 2 is 'an edge view of the same. Fig. 3 is an edge'view of a fragmentary portion of the central part of the rule. Fig. 4 is an end elevation, shown considerably enlarged.

beingl'had'to the accompanying drawings in Fig.' 5 isa cross sectional view of one member of the rule the slide being disconnected from the main bodyI to show more clearly its construction.

Referring tosaid figures', l and 2 designate the main body mem.

eis of the rule,

these` being similar and hinged together b y a rule joint 3, so that-When extended 1n vvided into alinement' the rule forms a straight bar of uniform cross sectional construction throughout.

Each body member is provided with an angular rabbet 4 extending throughout its length; these rabbets being alike and arranged to register when the rule members are in alinement. Within the rabbet is arranged to fit and The member is preferably of suitable cross sectional form to occupy the rabbet 4 and form in conjunction with the main members -a rule rectangular in cross section.

As an improved feature 'of construction, the slide .5 is provided-at its inner angle with an angular plate 6, one edge of which 7 projects Into a corresponding groove 8 in the rule body While the other edge 9 projects laterally and is bent at ri ht angles at a point outside the plane of t e slide and engages a corresponding groove 10 in the rule body. For convenience of construction the groove is formed by applying separate strips 11 o'f suitable cross sectional form'to. the main body members and securing them rigidly in position.

A marker designatedas a whole 12, is mounted. to slide upon the rule body; this marker conveniently4 taking the form of a clip internally shaped to iit upon the rule and and 14 which engage grooves 15 and 16 formed in the rule body members and slide member respectively. In order to hold the marker yieldably in any given position, a bent plate s ring 17 is interposedbetween the edge of t e rule body and the embracing part. of the cli which overlies said edge. The face side of) the marker is partially cut away as indicated at 18 and anindex Wire 19 extended across this cut away portion perpendicular to the longitudinal axis of the rule, so that it may be brought into register with any pair of graduation marks.

Each member of the rule body is provided With a graduated scale arranged adjacent to the edge of the rabbet alongwhich the slide member travels.. In the particular embodiment of the inventionshown the rule is diarts correspondin to the usual fractions o a foot, namely, into divisions corresponding to eighths, sixteenths, thirty-seconds and sixtyfo'urths. It is. to be articularl;r noted however that these divisions are not intended to rovided at eachend with inturned lips 13 slide, a slide member 5.

inches, quarter inches be `calibrated to actual measurements .but on the contrary are much larger and 'sufficiently so that the -smallest divisions and the numerals designating the same 'may be read cone veniently Without resorting to a magnifying.

instrument. It Will be noted that the subdivisions of each unit division are numbered regularly beginning at theleft hand end of each unit and it is also to be noted that, unlike lo arithmic sliderules, the divisions are of un' orm dimensions throughout the rule.

The slide member 5 is provided With a scale Which'is substantially a duplicate of a corresponding part of the scaleon the main mem- In other Words when the slide is' bers. shiftedtfo the extreme left of the rule, which corresponds to the zero position., the parts of the tWo scales then in register are identical.

' the third number found upon'the slide and' .using the instrument additions may be performed byshifting the slide so as to bring the index or zero line 20 into register With the iirst member on the main rule, then finding the second member to be added thereto on- -the slide and finally readingras the-sum of the two-numbers, that number on the main rule which is opposite. ln case three or `more numbers are to be added, after the sum of the first tWohas been found, the marker is.

shifted into position to retain this'number, the slide then shifted until its index line registers with the index'wire of the marker and the sum u on the main rule'as before, and s o on throug any number of-shifts Whihmay be made uponthe full lengthv of the rule.

Subtractions are of courseperformed in exactly the reverse manner.-

I clann as my invention:

1, In a slide rule 'comprising a main `body ,slide against lateral dis ',Way. comprising a rig 4the projectingedges of'said confining providedwith a uide Way extending throughoutits principa length, a scale laid off upon said main body in uniform-length unit divi sions and one or more series of uniformlength fractional divisions of each unit division, a slide mounted upon said guide Way and provided With a scale .essentially a d uplicate as to divisions of acorresponding part of the main body scale, said main body eing of tWo-partconstruction and the members thereof'united by a rule joint arranged to bring the respective portions of the guide Way into register and alinement When the mainmembers are in alinement. Y

- 2. In a slide'rule the combination of a l main body provided with a longitudinally extending' guide Way formed therein, a slide` fitting sald guide Way and means holding the slide against lateral, displacement fr om the Way, comprisin an angleplate rigidly se cured to t e sli e and projecting at its edge from the latter and an undercut groove formedV longitudinally in said Way'and receiving the edge of said angleplatef,

3. In a slide vrule the combination ofa main body provided with a longitudinally extendin "guide Way formed therein, a slide fitting said guide-way and. means holding the lacement from the t angled approximately Z haped plate secured to' the slide having both of its e'dges projectingtherelfrom, and undercut grooves formedin said main body, 'corresponding to and receiving ENRIK GRQNDA L. -Witnesses: `HARRY B. LANGLEY,

FRANK L.- BELlgNAR late.' 

